Montgomery thyroplasty. Case report focusing on endoscopic and

ACTA OTORHINOLARYNGOL ITAL 24, 226-233, 2004
Montgomery thyroplasty. Case report focusing on
endoscopic and functional findings
Case report di un paziente sottoposto ad intervento di Tiroplastica di I
tipo con protesi di Montgomery: rilievi endoscopici e funzionali
U. CESARI, C. FAGGIOLI, D. TESTA, O. VECCHIO, V. GALLI
ENT Department, University of Naples “Federico II”, Naples, Italy
Key words
Vocal cord paralysis • Surgical treatment • Thyroplasty •
Videoendoscopy
Summary
Parole chiave
Paralisi laringea • Trattamento chirurgico • Tiroplastica •
Videolaringostroboscopia
Riassunto
The case is described of a 58-year-old male with cord paralysis submitted to Montgomery thyroplasty, attention being
focused on the electro-acoustical findings. The usefulness
is underlined of these indices which provide the opportunity to establish the phonatory advantages and results of
this surgical procedure. Videolaryngostroboscopy and spectrographic analyses were carried out before and after
surgery. Phonatory results were, in fact, evaluable 24 hours
after surgery and found to be excellent whereas the perceptive evaluation and subjective symptoms were seen to be
comparable to those in normal subjects one week after
surgery.
Gli AA presentano una dettagliata analisi elettroacustica della voce di un paziente sottoposto ad intervento di tiroplastica
di I tipo secondo Montgomery sottolineando l’importanza e
l’utilità in particolare di alcuni indici che consentono di identificare in modo più specifico i vantaggi ed i risultati fonatori
di tale tecnica chirurgica. In sede di intervento è stata valutata la posizione assunta dalla corda vocale al momento dell’innesto protesico; gli Autori sottolineano la facilità di esecuzione della tecnica chirurgica nonché la mancanza di complicanze. Il paziente è stato valutato, prima e dopo l’intervento, mediante una videolaringostroboscopia, un’analisi spettrografica con sistema MDVP (Kay) che prevedeva il rilevamento dei
parametri di jitter (J), shimmer (Sh), NHR, VTI, DSH, DVB,
DUV, una valutazione percettiva della voce secondo la scala
GIRBAS, ed inoltre mediante un questionario di autovalutazione della propria voce per identificare il Voice Handicap Index (VHI). Dall’analisi di questi dati emerge che il risultato
fonatorio è ottimale e valutabile oggettivamente già a 24 ore
dall’intervento mentre la valutazione percettiva e la sintomatologia soggettiva sono assimilabili ai soggetti normali solo
ad una settimana dall’intervento chirurgico.
Introduction
cia implant 14, polydimethylsiloxane (PDMS-Bioplastique) 15. However, the phonatory results
achieved were not always maintained over time 16-20.
Type I Thyroplasty or medialisation of the vocal cord
is currently the first choice surgery, with longer-lasting phonatory results, to recover glottic competence
with passive correction of the cord position using implants of various materials. The sylastic implant designed by Montgomery has gained wide recognition
by many Authors 21 22 as the most valid technique currently available to simultaneously medialise the cord
and the arytenoid vocal process without severe complications. Its application is relatively simple and
rapid, it requires local anaesthesia, and on account of
the structure, no suture is required to keep it in place
and it rarely becomes dislodged 20 21. In addition, if
necessary, the implant can be readily removed with-
Unilateral paralysis in complete abduction causes severe glottic insufficiency that tends to show no spontaneous compensation in time (unlike unilateral
paralysis in a paramedian position). The voice of
these patients is typically low and breathy and due to
the marked phonatory strain frequent inspiration is
necessary.
Speech therapy alone cannot close the glottic gap;
for this reason, various corrective techniques have
been suggested, such as paraffin infiltration 1, homogenized cartilage 2, cartilage implant 3, the use of
pulverized bone in suspension 4, Tantalium in suspension 5, Teflon 6, Silicone 7, Hydron Gel 8, Gelfoam
paste 9, bovine collagen 10, autologous fat 11, autologous collagen 12, autologous fascia 13, autologous fas-
226
MONTGOMERY THYROPLASTY
out damaging the laryngeal tissue, and as the base of
the implant is of standard size, it can be replaced by
another of a different size without further intervening
on the insertion window. Some Authors 20 23 have
studied the phonatory results after this procedure, but
only a few of the electroacoustical parameters have
been assessed and no long-term follow-up results are
available.
Aim of the study
The aim of the study was to evaluate a case of cord
paralysis in complete abduction before and after
Montgomery thyroplasty, using stroboscopy and
spectroacoustical tests with MDVP to evaluate possible morphofunctional variations of the glottis and the
trends in the acoustical parameters over time, as well
as to identify the electroacoustical indices that provide the most useful information on the phonatory
dynamics after surgery.
Material and methods
G.C., a 58-year-old male, was admitted to our ward
with marked dysphonia, not associated with dysphagia, caused by a left cord paralysis in complete abduction secondary to total thyroidectomy performed
about 14 months earlier for multinodular goitre; the
patient reported having had speech therapy twice
weekly for 8 months with no improvement in the
symptoms. Montgomery type I thyroplasty was
planned. Before surgery and on the first, second,
third and seventh day after surgery, the patient underwent a series of tests comprising:
• laryngostroboscopy with Atmos stroboscopic
light with 90° rigid scope and a flexible fiberoptic scope. The latter was also used during surgery
to check that the paralysed vocal cord reached the
midline;
• spectrographic voice test, carried out with a Kay
4400 CSL system linked to a Personal Computer
and input level at 6/9, environment noise less than
30 dB, microphone at 20 cm from the patient’s
mouth, at an angle of 45°.
During the test the following data were recorded:
• an /A/ sustained for at least 6 seconds at an intensity ranging between 55 and 65 dB, after at least
3 trial runs, testing the middle 2 seconds for the
MDVP parameters applying a sampling rate at 50
kHz;
• the word “aiuole” with downsampling at 10 kHz;
• 10 seconds of spontaneous conversation.
On the basis of the spectrographic data, the following
parameters were evaluated (upper normal values are
given, in brackets, for each item):
227
– Jitter (1.04%) and Shimmer (3.81%), respectively, indicative of the average perturbations in
frequency and intensity;
– VAm (Variation Amplitude = 8.20%): mean percent variation in peak amplitude and is indicative
of voice intensity sustainment;
– FTRI (Frequency Tremor Intensity = 0.95%) and
ATRI (Amplitude Tremor Intensity = 4.37%), indicating, respectively, the depth of frequency and
amplitude tremors;
– NHR (Noise to Harmonics Ratio = 0.19), which
expresses the ratio, in absolute numbers, between
noise in the range 1500-4500 Hz and the harmonic energy in the range 70-4500 Hz (low frequency harmonics/noise ratio);
– VTI (Voice Turbulence Index = 0.06) ratio, in absolute terms, between noise in the range 28005800 Hz and the harmonic energy in the range 704500 Hz (harmonics/noise ratio on the high frequencies of the vocal spectrum);
– DUV (Degree of Unrecorded Voice = 0%), index
of the degree of voicelessness (irregular and prolonged interruptions with no detection of the fundamental frequency);
– DVB (Degree of Voice Breaks = 0%), index of
the degree of interruptions in sound;
– DSH (Degree of Subharmonics = 0%), index of
the degree of diplophonia;
• questionnaire for subjective VHI voice evaluation
(Jacobson modified by Luppi);
• in addition, 10 days after surgery, a CT scan of the
neck and larynx, without contrast medium, to
check that the implant was correctly positioned;
• four weeks after surgery a series of speech therapy sessions was carried out to maintain the good
quality of the voice achieved with surgery. The
aim of this therapy was to prolong the voice sustainment, by maintaing adduction and cord vibration. To combine phonation and articulation and
to make the patient’s voice more “natural”
“linked diphthongs” were used in only one
breath. Subsequently, vocal scales “with relaxed
voice” were suggested to teach the tone and intensity variations used in everyday speech.
Finally, 3 months after speech therapy, another electroacoustical examination was carried out to assess
any variations in voice performance.
Surgery was performed with the patient under local
anaesthetic, induced by infiltration with 1% Xylocaine and Adrenaline, sedation with i.v. Propofol at a
dose of 2 mg/kg/hour.
A horizontal skin incision was made on the neck
starting 2 cm from the midline to the anterior margin
of the sternocleidomastoid muscle, about 0.5 cm
above the lower margin of the thyroid cartilage, followed by an incision on the platysma, diastasis of the
sternohyoid muscles, exposure of the thyroid carti-
U. CESARI, ET AL.
lage, without cutting the sternohyoid and omohyoid
muscles. Identification of the Key Point (reference
point on the thyroid cartilage that marks the position
of the implant insertion window), marking of the four
corners with the window outline instrument, cutting
of the window and removal of the cartilage leaving
the inner perichondrium intact. After carefully stripping the intralaryngeal perichondrium, the implant
was selected with the use of a specific measuring calliper and inserted; no further dose of anaesthetic had
to be administered when the implant was inserted.
The correct positioning of the implant, the degree of
cord medialisation and the immediate phonatory results achieved were assessed during surgery using a
flexible fiberoptic laryngoscope. Suture of the deep
layers was carried out bringing the sternohyoid muscles together, on the midline, with single catgut
stitches, suction drainage was applied and the skin
was sutured.
Fig. 2A. Pre-operative MDVP evaluation: Parameter values - F0 = not determinable; Jitter = 7.2%; Shimmer =
13.5%; NHR = 3.5%; Vam = 28.5%; VTI = 3.2%; FTRI =
2.3%; ATRI = 5.2%; DSH = 2%; DVB = 2%; DUV = 1.2%
Results
PREOPERATIVE TESTS
Preoperative tests showed:
• at laryngostroboscopy (Fig. 1), a severe glottic
gap with attempted adductory compensation, by
the other vocal cord: in particular, the fixed vocal
cord appeared hypotonic and atrophic and even
below the glottic level. The right arytenoid presented slight luxation;
• Spectrographic test with MDVP parameters (Fig.
2A, B) showed the following phonatory assessFig. 2B. Pre-operative spectrography: noise overlaps signal. Sustained phonation is very short.
ment: F 0 = not assessable, Jitter 7.2%, Shimmer
13.5%, NHR 3.5, VAm 28.5%, VTI 3.2%, FTRI
2.3%, ATRI 5.2%, DSH 2% DVB 2%, DUV
1.2%.
Perceptual voice assessment (GIRBAS) showed level 3 for all parameters.
The VHI questionnaire showed a particularly high
score of 100, reflecting a clear difficulty in voice
emission.
Fig. 1. Pre-operative laryngostroboscopy: severe glottic
gap caused by paralysis of left vocal cord, which apeared
hypotonic, atrophic and even below glottic level. Right
arytenoid presented slight luxation.
POST-OPERATIVE EXAMINATION AT 24 HOURS
Laryngostroboscopy showed complete glottic closure with cord and arytenoid oedema (Fig. 4). This
confirmed the intra-operative findings with the flexible fiberoptic scope that demonstrated the favourable
outcome of surgery (Fig. 3), with no physical pain or
discomfort for the patient.
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MONTGOMERY THYROPLASTY
Fig. 4. Laryngostroboscopy 24 hours after surgery: complete glottic closure; oedema of left vocal cord and arytenoid.
Fig. 3. Intra-operative evaluation by flexible endoscope:
complete glottic closure.
Spectrographic tests showed the following already
good phonatory results (Fig. 5): F0 = 140 Hz, Jitter
3.5%, Shimmer 10.2%, NHR 0.17, VAm 17.2%,VTI
0.15%, FTRI 0.49%, ATRI 4.01%, DSH 0%, DVB
0%, DUV 0%.
The electro-acoustical parameters, one day after
surgery, confirmed the absence of diplophonia
(DSH) although the indices regarding disturbances in
frequency and intensity and the harmonics/noise ratio remained above normal threshold values.
The perceptual voice evaluation showed a clear reduction in the grade of dysphonia (G) from 3 to 1, as
also in the breathiness value (B), Instability (I) strain
(S); roughness (R) remained at score 3.
The VHI questionnaire confirmed a marked reduction
in phonation difficulty, although some psychophysical
difficulty persisted (score = 80) (lowest scores were
obtained for questions 11 to 20).
ASSESSMENT AT 48 AND 72 HOURS
Laryngostroboscopy: findings at 48 (Fig. 6) and 72
hours (Fig. 7) were comparable; cord oedema had
disappeared, but the arytenoid oedema remained;
Spectrographic tests: at 48 hours, the MDVP values
(Fig. 8) were as follows: F0 = 149 Hz, Jitter 2.5%,
Shimmer 8.5%, NHR 0.13, VAm 16.8%, VTI 0.11%,
FTRI 0.41%, ATRI 3.9%, DSH 0% DVB 0%,
DUV0%.
At 72 hours, the electro-acoustical parameters
showed further modifications (Fig. 9): F0 = 149 Hz,
Jitter 2.1%, Shimmer 7.5%, NHR 0.11, VAm 10.5.%,
VTI 0.04%, FTRI 0.38%, ATRI 3.1%, DSH 0% DVB
0%, DUV 0%. Briefly, the fundamental frequency re229
Fig. 5. MDVP assessment 24 hours after surgery: Parameter values.
F0 = 140 Hz; Jitter = 3.5%; Shimmer = 10.2%; NHR =
0.17%; VAm = 17.2%; VTI = 0.15%; FTRI = 0.49%; ATRI =
4.01%; DSH = 0%; DVB = 0%; DUV = 0%.
mained unchanged, while the other values showed
slight improvements, the most significant changes
being found for VAm and VTI.
Perceptual voice evaluation showed a score of 0 (normal) for G, I, B, A and S, and 1 for R.
VHI questionnaire still showed a score of 70, being
far from normal; in particular, the answers relating to
voice satisfaction were still negative, despite normal
spectrographic results.
U. CESARI, ET AL.
Fig. 6. Laryngostroboscopy 48 hours after surgery.
Fig. 8. MDVP evaluation 48 hours after surgery: parameter values.
F0 = 149 Hz; Jitter = 2.5%; Shimmer = 8.5%; NHR =
0.13%; VAm = 16.8%; VTI = 0.11%; FTRI = 0.41%; ATRI =
3.9%; DSH = 0%; DVB = 0%; DUV = 0%.
Fig. 7. Laryngostroboscopy 72 hours after surgery. Values are comparable: complete glottic closure; no oedema of left vocal cord but persistence of left arytenoid
oedema.
AT 7 DAYS AFTER SURGERY
Findings were as follows.
Laryngostroboscopy (Fig. 10): normal glottic closure, with no sign of laryngeal trauma or voice strain.
MDVP spectrographic tests: electro-acoustical values (Figs. 11A-B) showed no further changes: the
VAm and VTI values remained within the normal
range, whereas NHR, Jitter and Shimmer as well as
FTRI and ATRI still persisted above default values, 7
days after surgery, and did not present significant differences – GIRBAS values were all normal. VHI
scores were similar to those in normal subjects (58).
CT scan of the neck and larynx, without contrast
medium, 10 days after surgery (Fig. 12), confirmed
that the implant was correctly positioned.
The stroboscopic and electro-acoustical tests, carried
Fig. 9. MDVP evaluation 72 hours after surgery: parameter values.
F0 = 140 Hz; Jitter = 2.1%; Shimmer = 7.5%; NHR =
0.11%; VAm = 10.5%; VTI = 0.04%; FTRI = 0.38%; ATRI =
3.1%; DSH = 0%; DVB = 0%; DUV = 0%.
out 3 months later, showed no substantial variations,
thus confirming a satisfactory voice sustainment.
Discussion
The data emerging from our study offer some interesting considerations. The voice recovery achieved
with type I thyroplasty was immediate and satisfac-
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MONTGOMERY THYROPLASTY
Fig. 11B. Spectrographic evaluation 7 days after surgery:
harmonics are more clearly observed.
Fig. 10. Laryngostroboscopy 7 days after surgery: normal glottic closure, with no sign of laryngeal trauma or
voice strain.
Fig. 12. CT scan of neck without contrast medium during breathing: intrarotation of arytenoid and correct
position of implant are observed.
Fig. 11A. MDVP evaluation 7 days after surgery: there
were no further changes in electroacoustical values.
tory: in the case described here, use of a flexible endoscope, during surgery, showed the immediate
voice improvement achieved with the introduction
of the implant and the absence of any compensatory
mechanism. Laryngostroboscopy, with a fixed endoscope, confirmed the recovery of glottic efficiency
and showed a slight oedema of the relative arytenoids, the first two days after surgery. Noteworthy,
in this case, was atrophy of the paralysed vocal cord
and luxation of the opposite arytenoid: this was due,
in our opinion, to the continuous and prolonged attempts, by the organ, to compensate for the glottic
231
gap, thus creating an obstacle to complete recovery
following thyroplasty. In short, permanent alterations occur, due to strain, compromising perfect
voice recovery. Data from the electro-acoustical
voice tests confirm the endoscopic findings and also
provide more useful information on voice dynamics.
In particular, unlike our expectations, not all the
acoustic parameters allow adequate monitoring of
voice recovery. The Jitter and Shimmer values, in
particular, as well as the NHR values, remain impaired even when objective and subjective assessments indicate voice recovery. Numerous Authors 2427
have reported that the Jitter and Shimmer values
are often highly dependent upon muscle tension and
on the frequency and intensity of the voice, and cannot be considered a reliable means of evaluation that
offers statistically significant values denoting voice
improvement. On the contrary, a more evident voice
recovery can be seen from other parameters which
U. CESARI, ET AL.
have been recently introduced in quantitative voice
studies. A brief outline of their characteristics is given:
– VTI, expressing the harmonics/noise ratio, with
particular regard to the high frequencies (noise
ranging between 2800 and 5800 Hz and harmonic energy between 70 and 4500 Hz) of the vocal
spectrum, better reveals the reduction in the glottic gap; this appears to be higher, the greater the
adductory deficit and provides useful information
on the degree of voice efficiency reached.
– NHR (noise ranging between 1500 and 4500 Hz
and the harmonic energy distributed between 70
and 4500 Hz) did not show any substantial
changes during the study: it should be pointed out
that this index evaluates the inharmonic energy
located on low frequencies.
– DSH assesses diplophonia and is often difficult to
determine only from the sonagram, where it corresponds to the presence of one or more subharmonics among the true harmonics. It confirms the
reduction in diplophonia and allows evaluation
over time. In this study, normal values were observed, the day after surgery.
– DVB and DUV show the segments of voicelessness better as well as their reduction: these values
had already reached normal threshold levels, the
day after surgery.
– Shimmer presents a trend that directly correlates
with Jitter, and does not offer any specific information: both remained impaired after surgical recovery and after the patient reported complete
voice recovery.
– VAm, instead, shows the clearest changes as far
as concerns voice improvement. This value is inversely correlated to the stability of voice intensity, and is particularly indicative of voice sustainment.
– FTRI and ATRI show a reduction directly related to a reduction in the glottic gap and consequent voice improvement.
References
Conclusions
The present investigation is limited to only one case
and, therefore, does not allow generalisation; however, the evolution in the electro-acoustical voice parameters, during follow-up provides useful information
on glottic status after type I thyroplasty. First of all, we
confirm the need for quantitative and multiparametric
electro-acoustical tests, in this type of surgery, which
are still not widespread in clinical practice, in order to
reliably assess voice improvement and to provide a
useful legal medicine aid for the operating surgeon.
Many of the cases of cord paralysis found in clinical
practice are the outcome of previous surgery (17-46%)
28
. No detailed voice studies are available, as yet, on
the results achieved with Montgomery thyroplasty; in
a very recent study 20, Peretti et al. refer only to TMF,
J and Sh. Our data show that the J and Sh values are
extremely non-specific and of little significance, while
VAm and VTI allow good monitoring of voice recovery, as seen in Table I (comparative assessment of the
changes in J, Sh and Vam, in the pre-operative evaluation, and at 24, 48, and 72 hours, respectively, after
surgery). Data from the questionnaire, completed by
the patient, are interesting: up to three days after
surgery, the VHI data did not correspond with the good
recovery indicated by the electro-acoustical data and
evident at endoscopy; the data are indicative of the
patent’s social discomfort caused by the psychological
impact of his own voice. Only 7 days after surgery
were the VHI values within normal limits and in keeping with the data from the subjective evaluation. It appears that the rapid voice recovery, perceived by the
physicians during and immediately after surgery, as
confirmed by the spectrographic data, does not meet
with a correct perception of his voice, by the patient.
A few days are necessary for the patient to adapt to the
new, more efficient voice tone. We suggest speech
therapy in order to maintain the voice recovery
achieved, above all to prevent compensatory voice
mechanisms that the patient might instinctively adopt
even with the new and more efficient glottic closure.
5
1
Brunings W. Uber eine neue Behandlungsmethode der
Rekurrenslahmung. Ver Deutsch Laryngol 1911;18:93-151.
6
2
Arnold GE. Vocal rehabilitation of paralytic dysphonia: I.
Cartilage injection into a paralysed vocal cord. Arch Otolaryngol 1955;62:1-17.
7
3
Waltner JC. Surgical rehabilitation of voice following
laryngo-fissure. Arch Otolaryngol 1958;67:99-101.
4
Goff WF. Laryngeal adductor paralysis treated by vocal
cord injection of bone paste: a preliminary investigation.
Trans Pac Coast Otoophthalmol Soc 1960;41:77-88.
8
9
Arnold GE. Vocal rehabilitation of paralytic dysphonia: VI.
Further studies of intracordal injection materials. Arch
Otolaryngol 1961;73:290-4.
Arnold GE. Vocal rehabilitation of paralytic dysphonia: IX.
Technique of intracordal injection. Arch Otolaryngol
1962;76:358-68.
Rubin HJ. Pitfalls in treatment of disphonias by intracordal
injection of synthetics. Laryngoscope 1965;75:1381-95.
Kresa Z, Riems J, Wichterle O. Hydron-gel implants in vocal cord. Acta Otolaryngol 1973;76:360-5.
Schramm VL jr, Lavorato AS. Gelfoam paste injection for
vocal cord paralysis: temporary rehabilitation of glottic in-
232
MONTGOMERY THYROPLASTY
10
11
12
13
14
15
16
17
18
19
20
competence. Laryngoscope 1978;88:1268-73.
Ford CN, Bless DM. Clinical experience with injectable
collagen for vocal fold augmentation. Laryngoscope
1986;96:863-9.
Mikaelian DO, Lowry LD, Sataloff RT. Lipoinjection for
Unilateral Vocal Cord Paralysis. Laryngoscope
1991;101:465-8.
Ford CN, Staskowski PA, Bless DM. Autologous collagen
vocal fold injection; a preliminary clinical study. Laryngoscope 1995;105:944-8.
Rinkanen H. Vocal fold augmentation by injection of autologus fascia. Laryngoscope 1998;108:51-4.
Tsunoda K, Niimi S. Autologous transplantation of fascia
into the vocal fold. Laryngoscope 2000;110:680-2.
Sittel C, Thumfart WF, Pototschnig C, Wittekindt C, Eckel
HE. Textured polydimethylsiloxane elastomers in the human larynx. Safety and efficiency. J Biomed Mater Res
2000;53:646-50.
Isshiki N. Recent modifications in thyroplasty type I. Ann
Otol Rhinol Laryngol 1989;98:777-9.
Ricci Maccarini A, Casolino D, Vitali L. Classificazione ed
indicazioni delle laringoplastiche. Giornate di Fonochirurgia, Cervia 2-4 maggio, 1996.
Accordi M, Tesserin F, Accordi A, Santoni A. La Tiroplastica tipo I modificata nella terapia chirurgica delle paralisi
unilaterali della laringe. Acta Otorhinolaryngol Ital
1999;19:226-34.
Woo P. Arytenoid adduction and medialization laryngoplasty. Otolaryngol Clin North Am 2000;33:817-39.
Peretti G, Provenzano L, Piazza G, Giudice M, Antonelli
AR. Risultati funzionali dopo tiroplastica di I tipo con
protesi di Montgomery. Acta Otorhinolaryngol Ital
n Received October 2, 2003
Accepted May 12, 2004
n Address for correspondence: Dr. U. Cesari, Via G. Serra
32, 80132 Napoli, Italy. Fax: +39 081 7641391. E-mail:
[email protected]
233
21
22
23
24
25
26
27
28
2001;21:156-61.
Montgomery WW, Montgomery SK. Montgomery thyroplasty implant system. Ann Otol Rhinol Laryngol
1997;106(Suppl 170):1-16.
McLean-Muse A, Montgomery WW, Hillman RE, Varvares
M, Bunting G, Doyle P, et al. Montgomery thyroplasty implant for vocal fold immobility: phonatory outcomes. Ann
Otol Rhinol Laryngol 2000;109:393-400.
Magnani M, Accordi M, Casolino D, Ricci Maccarini A. La
tiroplastica di medializzazione cordale. In: Casolino D, editor. Le disfonie: fisiopatologia clinica ed aspetti medico-legali. Relazione Ufficiale LXXXIX Congresso Nazionale
SIO e Ch CF. San Benedetto del Tronto. Pisa: Pacini Editore; 2002. p. 501-515.
Biondi S, Zappalà M, Amato G. La spettrografia della voce.
Acta Phon Lat 1990;12:199-236.
Di Nicola V, Fiorella ML, Luperto P, Staffieri A, Fiorella R.
La valutazione obiettiva della disfonia. Possibilità e limiti.
Acta Otorhinolaryngol Ital 2000;21:10-21.
Di Nicola V, Bellotti R, Fiorella ML, Luperto P, Fiorella R.
MDVP. Introduzione e metodologia. Acta Phon Lat
2002;24:94-104.
De Colle W, Ricci-Maccarini A. Acoustic analysis by Kay
CSL 4300 in voice assessment. Work-book of Workshop at
the 6th I.A.P. Symposium. Venezia-Abano Terme; 2000. p.
19-22.
Piemonte M, Rugiu MG, Miani G. Disturbi neurologici e
muscolari della laringe. In: Casolino D, ed. Le disfonie: fisiopatologia clinica ed aspetti medico-legali. Relazione Ufficiale LXXXIX Congresso Nazionale SIO e Ch CF. San
Benedetto del Tronto: Pisa: Pacini Editore; 2002. p. 468492.